Controller for machine tool

Abstract

To provide a controller for a machine tool capable of shredding chips and capable of performing machining by cutting correctly without implementation of a so-called finishing process. A controller for a machine tool includes: an oscillation command generation unit that generates an oscillation command for causing a work and a tool to oscillate relative to each other in a radial direction of the work based on a condition for oscillation; a movement command generation unit that generates a movement command for causing the work and the tool to move relative to each other for thread cutting of the work; an adder that adds the oscillation command and the movement command; and a determination unit that predetermines whether the oscillation command is to be added to the movement command, is which the adder outputs a superimposed command configured to include one or more types of machining patterns combining an arbitrary number of a total movement command with the oscillation command added, and an arbitrary number of a total movement command without the oscillation command added, in accordance with a result of determination by the determination unit.

What is claimed is: 
     
       1. A controller for a machine tool used for thread cutting on a work by repeating motion of moving a tool in a rotary axis direction in synchronization with rotation of the work a plurality of times, while cutting-in in a radial direction, the controller comprising:
 an oscillation command generation unit that generates an oscillation command for causing the work and the tool to oscillate relative to each other in the radial direction of the work based on a condition for oscillation; 
 a movement command generation unit that generates a movement command for causing the work and the tool to move relative to each other for thread cutting of the work; 
 an adder that adds the oscillation command and the movement command; and 
 a determination unit that predetermines whether the oscillation command is to be added to the movement command, wherein the adder outputs a superimposed command configured to include one or more types of machining patterns that combine: 
 a plurality of total movement commands, each of the plurality of total movement commands including the movement command and the oscillation command, and 
 a plurality of other total movement commands, each of the plurality of other total movement commands including the movement command without the oscillation command, 
 wherein the superimposed command results in a repeated order where each total movement command is followed by a corresponding other total movement command, 
 in accordance with a result of determination by the determination unit, and 
 wherein a path of each total movement command intersects a corresponding path of the following other total movement command in the radial direction, 
 wherein as the paths generated by the total movement commands and the corresponding paths generated by the other total movement commands increase, the tool moves deeper and closer to the center of the work, resulting in the thread cutting on the work. 
 
     
     
       2. The controller for the machine tool according to  claim 1 , wherein the determination unit inspects a machining program for the thread cutting on the work, and determines whether the oscillation command is to be added to the movement command. 
     
     
       3. The controller for the machine tool according to  claim 1 , wherein the determination unit outputs a command so as to be composed of the total movement command with the oscillation command added, until a cut made by the relative oscillation between the work and the tool in the radial direction of the work reaches the bottom of a thread groove as a target of the thread cutting, and outputs a command so as to be composed of the total movement command without the oscillation command added, after the cut made by the relative oscillation between the work and the tool in the radial direction of the work reaches the bottom of the thread groove as the target of the thread cutting. 
     
     
       4. The controller for the machine tool according to  claim 1 , wherein the oscillation command generation unit generates the oscillation command in such a manner that a part already machined by a different cutting-in process is absent in each cutting-in process with oscillation of causing the work and the tool to oscillate relative to each other in the radial direction of the work. 
     
     
       5. The controller for the machine tool according to  claim 1 , wherein the oscillation command generation unit generates the oscillation command for applying oscillation at an oscillation frequency obtained by multiplying the rotation speed of a spindle axis to rotate the work by a predetermined constant. 
     
     
       6. The controller for the machine tool according to  claim 1 , wherein the oscillation command generation unit generates the oscillation command in such a manner that, as the thread cutting on the work proceeds, the amplitude of the relative oscillation between the work and the tool in the radial direction of the work becomes greater for each path. 
     
     
       7. The controller for the machine tool according to  claim 1 , wherein the oscillation command generation unit generates the oscillation command in such a manner that, as the thread cutting on the work proceeds, an offset of the start position of the relative oscillation between the work and the tool in the radial direction of the work becomes greater for each path. 
     
     
       8. The controller for the machine tool according to  claim 1 , wherein the oscillation command generation unit generates the oscillation command in such a manner that each cutting-in process involving oscillation does not include a part already machined by a different cutting-in process involving oscillation, such that paths of each of the cutting-in processes involving oscillation do not intersect. 
     
     
       9. The controller for the machine tool according to  claim 1 , wherein all oscillations based on the oscillation command have a same phase.